Showing papers in "IEEE Journal of Quantum Electronics in 1986"

Statistical optics

Abstract: Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

Gain and the threshold of three-dimensional quantum-box lasers

Abstract: Gain and threshold current density are analyzed for quantum-box lasers where electrons are confined in quantum well three-dimensionally, based on the density-matrix theory of semiconductor lasers with relaxation broadening. The electronic dipole moment and its polarization dependence are first analyzed, and it is shown that the gain becomes maximum when the electric field of light is parallel to the longest side of the quantum box. Calculated gain is about 10 times that of bulk crystal for 100 A × 100 A × 100 A GaAs/Ga 0.8 Al 0.2 As quantum box, and 15 times for Ga 0.47 In 0.53 As/InP quantum box with the same size, respectively. The threshold current density are 45 A/cm2and 62 A/cm2for GRINSCH GaAs/(Ga 0.8 Al 0.2 As-Ga 0.4 Al 0.6 As) and Ga 0.47 In 0.53 As/(Ga 0.28 In 0.72 As 0.6 P 0.4 -InP), respectively, where for the GaInAs/ GaInAsP/InP system the intervalence band absorption and nonradiative recombinations have been assumed to be the same as those obtained for bulk crystals experimentally. These results show the possibility of remarkable reduction in the laser threshold by the quantum-box structures.

Physics and applications of Ge x Si 1-x /Si strained-layer heterostructures

Abstract: This paper reviews recent advances in our current level of understanding of the physics underlying transport and optical properties of Ge x Si 1-x /Si strained-layer heterostructures. Included are discussions of critical (maximum) layer thicknesses, effects of coherency strain on the bandgaps of both Si and Ge x Si 1-x and the influence of layer strains on the band alignments of Ge x Si 1-x /Si strained-layer heterostructures. Transport studies will center on the modulation doping results of both n and p type heterostructures. Indeed, these earlier transport studies provided essential information which led to an understanding of the band-alignment in these strained layer heterostructures. Recent measurements of the indirect bandgap of Ge x Si 1-x strained layers on

Resonant tunneling through double barriers, perpendicular quantum transport phenomena in superlattices, and their device applications

Abstract: New results on the physics of tunneling in quantum well heterostructures and its device applications are discussed. Following a general review of the field in the Introduction, in the second section resonant tunneling through double barriers is investigated. Recent conflicting interpretations of this effect in terms of a Fabry-Perot mechanism or sequential tunneling are reconciled via an analysis of scattering. It is shown that the ratio of the intrinsic resonance width to the total scattering width (collision broadening) determines which of the two mechanisms controls resonant tunneling. The role of symmetry is quantitatively analyzed and two recently proposed resonant tunneling transistor structures are discussed. The third section deals with perpendicular transport in superlattices. A simple expression for the low field mobility in the miniband conduction regime is derived; localization effects, hopping conduction, and effective mass filtering are discussed. In the following section, experimental results on tunneling superlattice photoconductors based on effective mass filtering are presented. In the fifth section, negative differential resistance resulting from localization in a high electric field is discussed. In the last section, the observation of sequential resonant tunneling in superlattices is reported. We point out a remarkable analogy between this phenomenon and paramagnetic spin resonance. New tunable infrared semiconductor lasers and wavelength selective detectors based on this effect are discussed.

Quantum well lasers--Gain, spectra, dynamics

Abstract: We discuss a number of theoretical and experimental issues in quantum well lasers with emphasis on the basic behavior of the gain, the field spectrum, and the modulation dynamics It is revealed that the use of quantum well structures results in improvement of these properties and brings several new concepts to optical semiconductor devices

All-silicon active and passive guided-wave components for λ = 1.3 and 1.6 µm

Abstract: End-coupled planar and channel waveguides at 1.3 μm have been demonstrated in single-crystal Si layers grown epitaxially on heavily doped Si substrates, and an optical power divider consisting of intersecting channels was designed and fabricated. Optical switches in Si based on electrooptic, acoustooptic, and optical-injection mechanisms are described. The advantages of all-silicon integrated optical components are discussed.

Zero-dimensional "excitons" in semiconductor clusters

Abstract: Semiconductor crystallites of characteristic dimension \sim20-100 A can be made by precipitation in liquids and dielectrics. These crystallites have bulk-like internal lattices. The optical spectra show partially resolved discrete features that result from carrier spatial confinement in three dimensions. Spectral shifts of more than 1 eV are observed. The electronic wavefunctions of small crystallites are discussed within the effective mass approximation. The pattern of discrete hole states is qualitatively different in small crystallites than in slab superlattices. In small CdS crystallites, luminescence is observed from trapped carriers that may be in localized surface states. The recombination emission is strongly coupled to crystallite phonons.

Subpicosecond electrooptic sampling: Principles and applications

Abstract: This paper reviews the principles and applications of electrooptic sampling for the characterization of repetitive ultrafast electrical transients. Electrooptic sampling is an electric field sensitive technique that utilizes ultrashort optical pulses as "sampling gates" via the Pockels effect in electrooptic media and has demonstrated subpicosecond temporal resolution and microvolt sensitivity. The technique can be adapted to characterize a wide variety of picosecond electronic devices such as field-effect transistors and photodetectors as well as probe complete integrated circuits with high temporal and spatial resolution.

Electronic states in semiconductor heterostructures

Abstract: This paper describes the electronic energy levels of semiconductor heterostructures within the envelope function scheme. Quantum well and superlattice electronic states are calculated and discussed, especially the in-plane dispersion relations. The Coulombic bound states in heterostructures (impurities, excitons) are then discussed. Finally, we present a brief overview of the effect of a static electric field on the carrier and exciton energy levels in semiconductor quantum wells.

Electrooptic sampling in GaAs integrated circuits

Abstract: Electrooptic sampling has been shown to be a very powerful technique for making time-domain measurements of fast electronic devices and circuits. Previous embodiments relied on a hybrid connection between the device under test and a transmission line deposited on an electrooptic substrate such as LiTaO 3 . The hybrid nature of this approach leads to device packaging difficulties and can result in measurement inaccuracies and performance degradation at very high frequencies. Since GaAs is electrooptic and an attractive material for high speed devices, we have devised an approach of direct electrooptic sampling of voltage waveforms in the host semiconductor. In this paper, we review the principles and limitations of electrooptic sampling and discuss this new noninvasive technique for electronic probing with applications to characterizing high speed GaAs circuits and devices.

Linewidth determination from self-heterodyne measurements with subcoherence delay times

Abstract: The behavior of the power spectrum of an external cavity semiconductor laser has been studied using a delayed self-heterodyne interferometric technique that uses delay times less than the laser's coherence time. Experimental results show that the resulting power spectrum is consistent with the theoretical model. However, there is evidence that additional frequency fluctuations are present that cause the delta function portion of the power spectrum to have a finite width.

Soliton propagation in long fibers with periodically compensated loss

Abstract: With computer simulation, we study soliton propagation in an all-optical, long-distance communications system where fiber loss is periodically compensated by Raman gain We find that distortion of the transmitted pulses from true solitons shows a peak near z_{0} = L/8 where L and z 0 are the amplification and soliton periods, respectively We also describe optimal system design based on the exceptional pulse stability and low soliton powers obtained in the region z_{0} \gg L/8 Typical amplification periods are in the range 30-50 km, pump powers are less than 100 mW, and for bit rates in the 10 GHz range, time average signal powers are at most a few milliwatts The single-channel rate-length product for error rate less than 10-9is \sim29 000 GHz Km Finally, we show that in the gain-compensated system with wavelength multiplexing, soliton-soliton collisions produce random modulation of individual pulse velocities Nevertheless, multiplexing can yield rate-length products greater than 300 000 GHz km

A bird's-eye view on the evolution of semiconductor superlattices and quantum wells

Abstract: Following the past seventeen-year developmental path in the research of semiconductor superlattices and quantum wells, significant milestones are presented with emphasis on experimental investigations in the device physics of reduced dimensionality performed in cooperation with the materials science of heteroepitaxial growth.

Electric-field dependence of linear optical properties in quantum well structures: Waveguide electroabsorption and sum rules

Abstract: We summarize the electric-field dependence of absorption and luminescence in quantum wells for fields perpendicular to the layers, present extended discussion of electroabsorption spectra and devices in waveguide samples, and derive sum rules for electroabsorption. Optical bistability, self-linearized modulation, and optical level shifting are demonstrated in self-electrooptic effect device configurations, with good modulation contrast and polarization-dependent properties. The electroabsorption spectra enable quantitative comparison of theory and experiment for absorption strengths in quantum wells with field. The sum rules enable excitonic effects to be included in the comparison, and good agreement is seen. One sum rule is also more generally applicable to electroabsorption in semiconductors.

Second-harmonic generation to 2048 Å in Β-Ba 2 O 4

Abstract: \Beta -BaB 2 O 4 has been found to be phase matchable for second-harmonic generation down to 2048 A at room temperature. Sellmeier's equations, which are highly accurate from 1.064 μm to 2050 A, are reported.

Integrated optics components and devices using periodic structures

Abstract: The selected research activities on integrated optics components and devices using periodic structures are reviewed, with emphasis on the authors' works employing the electron-beam writing technique. The periodic structures include static gratings and dynamic ones produced through acoustooptic (AO) and electrooptic (EO) effects. They provide a variety of passive functions and effective means for guided-wave control. The review is made from the integration point of view, including the most recent results. First, the theoretical fundamentals are outlined and the electron-beam writing techniques, including the writing system, are discussed. Next, passive components (grating deflectors, filters, lenses, couplers, etc.) and elements for guided-wave controlling and detecting (AO and EO grating elements and photodetectors) are described. Then, integrated optic devices, i.e., wavelength demultiplexers, RF spectrum analyzers, optical disk pickup, etc., are presented. Finally, the possibility of future applications is discussed.

Improved coupled-mode equations for dielectric guides

Abstract: An improved version of coupled-mode equations for parallel dielectric waveguides has been derived by using a newly found relationship that connects the propagation constants of the individual guides to the coupling coefficients via an overlap integral that measures the guides' proximity. The four parameters of these new coupled equations are simple functions of essentially one single quantity: the asynchronism of the individual guides properly normalized.

Stimulated Wood's anomalies on laser-illuminated surfaces

Abstract: Spontaneous, highly periodic, often permanent surface gratings or "ripples" can develop on the surface of almost any solid or liquid material illuminated by a single laser beam of sufficient intensity, under either pulsed or CW conditions. The grating periods are such that the incident laser beam is diffracted into a tangential wave which skims just along or under the illuminated surface. These spontaneously appearing surface ripples are generated by a runaway growth process analogous to stimulated Brillouin or Raman scattering or small-scale self focusing, but having many of the same properties as Wood's anomalies in diffraction gratings. Hence, it seems appropriate to refer to these spontaneous surface structures as "stimulated Wood's anomalies."

Instability of semiconductor lasers due to optical feedback from distant reflectors

Abstract: We explain an istability occurring in continuously operating lasers due to moderate feedback from distant reflectors. This instability occurs despite the fact that the laser is stable with respect to small deviations from steady-state operation. It is the result of finite phase and carrier number changes caused by fluctuations in spontaneous emission. We predict several properties that agree with recent experimental observations: 1) the instability only occurs when the laser reaches a steady state that maximizes coherent feedback and laser light intensity; 2) the instability vanishes at strong feedback levels; and 3) at moderate feedback levels, the laser will be nearly stable at threshold, but unstable when operated well above threshold. The latter behavior results in a nonlinear "kinked" shape in the light versus current relation.

Phonons in semiconductor superlattices

Abstract: Experimental results on phonons in semiconductor super-lattices are almost all from Raman scattering measurements. The superlattice system most studied is GaAs-Ga 1-x Al x As, and in the best-understood geometry the phonons are longitudinal modes with wave vectors perpendicular to the

Design considerations for a femtosecond pulse laser balancing self phase modulation, group velocity dispersion, saturable absorption, and saturable gain

Abstract: This paper describes the design and operating characteristics of a femtosecond pulse ring dye laser that employs the combined effects of self phase modulation, group velocity dispersion, saturable absorption, and saturable gain to generate pulses as short as 27 fs.

High-speed InGaAsP constricted-mesa lasers

Abstract: Recently, the bandwidths of semiconductor lasers, detectors, and optical transmission systems have been dramatically increased. The considerations used to achieve a record 26.5 GHz bandwidth in a 1.3 μm InGaAsP laser at -60°C are described here. The small-signal modulation characteristics of a number of different laser structures are compared. Several large-signal modulation experiments are described with emphasis on the laser response to 8 Gbit/s modulation.

Integrated optics

Abstract: Integrated OpticsIntegrated Optics and Optical SwitchingIntegrated Optics: Theory and TechnologyIntroduction to Integrated OpticsElements of Photonics, Volume IIEncyclopedic Handbook of Integrated OpticsOptical Fiber Communication Conference and Sixth International Conference on Integrated Optics and Optical Fiber CommunicationIntegrated Optical Circuits and ComponentsIntegrated OpticsAdvances in Integrated OpticsFundamentals of Fibre Optics in Telecommunication and Sensor SystemsIntegrated OpticsIntegrated Optics, Microstructures, and SensorsMulti-Photon Quantum Information Science and Technology in Integrated OpticsIntegrated Optics, Microstructures, and SensorsIntegrated PhotonicsOptics and LasersA Consideration of Possibilities and Difficulties in Passive Circuits in Integrated OpticsSemiconductor Integrated Optics for Switching LightIntegrated OpticsIntegrated OpticsAdvanced Materials for Integrated Optical WaveguidesIntroduction to Semiconductor Integrated OpticsCommercial Integrated OpticsIntegrated OpticsIntegrated Optics and MicrostructuresElectromagnetic Principles of Integrated OpticsIntegrated Optics and Micro-Optics with PolymersIntroduction to Integrated OpticsIntegrated Optics SuppliersIntegrated Optics: Theory and TechnologyDiffractive Optics and Optical MicrosystemsIntegrated Optics and OptoelectronicsFiber and Integrated OpticsEncyclopedic Handbook of Integrated OpticsFirst International Conference on Integrated Optical Circuit EngineeringIntegrated OpticsIon Exchange in Single Crystals for Integrated Optics and OptoelectronicsOptics and LasersIntegrated Optics: Devices, Materials, and Technologies

Noise analysis of injection-locked semiconductor injection lasers

Abstract: The noise of injection-locked semiconductor lasers is analyzed by rate equations including the spontaneous emission noise. The side mode suppression and the relative intensity noise (RIN) of the locked laser (slave laser) are given for different wavelengths detuning between the master and slave laser and for different linewidth enhancement factors α. For large α, locking is difficult to achieve, whereas extremely low noise may be obtained for injection-locked lasers with a low linewidth enhancement factor.

Analysis of picosecond pulse shape synthesis by spectral masking in a grating pulse compressor

Abstract: This paper analyzes the synthesis of arbitrarily shaped optical pulses by spectral filtering in a fiber-and-grating pulse compressor. Spectral filtering of phase and amplitude is achieved by masking the spatially dispersed frequency components within the compressor. We show that the spectral filter is the convolution of the mask with the beam's transverse intensity profile. We discuss the effect of diffraction from the features of the physical mask, and show how finite spatial resolution limits the range of attainable temporal profiles. The fundamental limitation on spectral resolution is derived. Spectra and temporal pulse shapes corresponding to a variety of physical masks are calculated and are found to be in excellent agreement with experiments done with compressed pulses from a mode-locked Nd: YAG laser.

Architectures for large nonblocking optical space switches

Abstract: This paper introduces three architectures for optical space switches that are based on a multiplicity of fiber interconnected optical components. The architectures eliminate the need for optical waveguide Crossovers and reduce the complexity required in the individual elements. The architectures are strictly nonblocking and allow for easy control and routing. Architecture type 1 exhibits a low system attenuation and a high system signal-to-noise ratio for very large switch dimensions. Architectures 2 and 3 are alternatives for realizing broadcast and point-to-point architectures.

Low dark current GaAs metal-semiconductor-metal (MSM) photodiodes using WSi x contacts

Abstract: We present the fabrication and characterization of metal-semiconductor-metal (MSM) photodiodes using the same undoped GaAs layer that is used as a buffer layer in the epitaxial structure for GaAs field effect transistors (FET's). To study the dark current mechanism, various metal electrodes used for Schottky contacts are examined. A drastic V-shape relationship between the dark current of MSM photodiode and the Schottky barrier height is found. An extremely low dark current (a few nanoamperes) in the MSM photodiode is obtained by using tungsten silicide as electrode metal. It is concluded that the dark current is a function of a rivalry relation between the electron injection at the cathode and the hole injection at the anode. The internal gain of the MSM photodiode with tungsten silicide contacts is found, and possible mechanisms are discussed. A flat frequency response up to 1.3 GHz is obtained. The results shows the feasibility of MSM photodiodes for use as photodetectors with low minimum detectable power, and their applicability to monolithic integration with FET circuits.

Optically nonlinear waves in thin films

Abstract: A new treatment of the behavior of TE nonlinear waves in an optically nonlinear film is given. The new mathematical results are expressed in terms of the physical parameters of the system and represent a straightforward way to introduce the necessary Jacobian elliptic functions. The optical nonlinearity is of the Kerr type and the numerical calculations are performed for a self-focusing medium. Dispersion curves labeled with optical power density at the lower film boundary, detailed plots of the variation of electric field amplitude as the wave number changes, and details of the power distribution across the guide are given. Since two values of a wave number can exist for the same power level and power thresholds exist, the system is of device interest in the area of optical switching.

Doping superlattices ("n-i-p-i crystals")

Abstract: Semiconductors with doing superlattices exhibit a number of unique features by which they differ from uniform bulk crystals as well as from semiconductors with a compositional superlattice. The properties which make them particularly appealing as a new kind of semiconductor are tunability of carrier concentration, bandgap, two-dimensional subband structure, and recombination lifetimes, in combination with an enormous flexibility in tailoring. Moreover, the choice of host materials is not restricted by interface- or lattice-matching problems. The possibility of varying conductivity, absorption coefficient, optical gain, and luminescence spectra by light or external electrical potentials implies new concepts for photodetectors, tunable light sources, optical amplifiers, and modulators. The long recombination lifetimes result in large low-power nonlinearities of the optical absorption coefficient and the refractive index. These properties offer applications for saturable absorbers and bistable optical devices. In this paper the basic concept of doping superlattices and experiments which have provided its verification will be reviewed first. New physical phenomena and possible device applications will then be discussed. Finally, we will report some recent results of extensions of the concept to "hetero n-i-p-i's," obtained by periodic modulation of composition superimposed on the periodic n-i-p-i doping profile.